EOSC 116 Module B EXAM PRACTICE QUESTIONS AND CORRECT DETAILED ANSWERS

EOSC 116 Module B EXAM PRACTICE QUESTIONS AND CORRECT DETAILED ANSWERS How old do astronimical observations put the universe at? - ANSWER- 12-14 billion years How long ago did the Earth and Solar System form? - ANSWER- 4.5-4.6 billion years ago When was the surface of the planet cool enough to support liquid water? - ANSWER- 3.8 Ga based on findings of water-lain sediments dating back to that age. Define biosphere - ANSWER- a thin veneer of life that surrounds the surface of our planet; it penetrates a little way into the crust and is also present in the atmosphere. The biosphere interacts with the other Earth systems including the lithosphere (the solid Earth), hydrosphere (liquid water), cryosphere (ice), and the atmosphere (air). Describe the Panspermia Hypothesis of how life developed on earth - ANSWER- Life was Brought to Earth. It is known that certain meteorites and comets contain organic molecules useful for life's processes. It is very likely that some of these organic molecules were brought to Earth by impacts of such extraterrestrial bodies with the Earth. It has also been suggested that life itself may have been transported to our planet in the form of microbes. However, evidence of living microbes in extraterrestrial objects has yet to be found. Describe a Earth-based Origin: Ocean Margin Hypothesis for how life developed on earth - ANSWER- Alexander Oparin () and J.B.S. Haldane () independently proposed a hypothesis that conditions on the primitive Earth favored chemical reactions that produced organic compounds from inorganic material. These organic compounds were possible precursors of cells from which primitive living things could develop. Name and describe an experiment that tested the Earth-based Origin: Ocean Margin Hypothesis - ANSWER- In a glass vessel he mixed the gases thought to be constituents of the early Archean atmosphere, methane (CH4), ammonia (NH3), water (H2O), and hydrogen (H2). To this he added an electric spark to represent the turbulent Archean atmosphere. Because the Earth's ozone layer had yet to develop at that time, the Earth's surface was receiving high UV radiation from the Sun. These conditions were simulated by bathing the apparatus in ultraviolet light. After 3 days of running their experiment, Miller and Urey found that 20 amino acids (the building blocks of proteins) had formed from the basic constituents. This early experiment established that it is possible to produce organic molecules via abiogenic processes. How do we define life? - ANSWER- it has to demonstrate 1) metabolism, 2) growth, 3) an ability to reproduce, and (perhaps from a paleontologists view point) 4) some sort of evolution with changing environmental conditions. To produce entities that might be capable of demonstrating these qualities, simple organic molecules such as amino acids have to be brought together to form more complex molecules. This process is called polymerization. Two different hypotheses have been suggested for how polymerization may have happened. Name the two hypotheses behind polymerization - ANSWER- A. Sidney W. Fox () suggested it may have happened in a rock pool by the side of the ocean that slowly gets heated in the sun and starts to evaporate, concentrating the amino acids present in the seawater. As the concentration builds, some of the amino acids start to form linkages with each other and produce chains of amino acids. B. Clays may have had an important role to play in that microscopic clay may have attracted amino acids via distince electrical charges which attraced amino acids which also carry a distinct electrical charge. By bringing amino acids into close contact along their surface, clays may have acted as a template for the formation of complex molecules. Describe the Earth-based Origin: Deep Ocean Hydrothermal Vent Hypothesis for how life developed on earth - ANSWER- Oceanic hydrothermal vents have only been recently discovered. They form where oceanic water seeps through cracks in the seafloor and is heated by magma sources at depth - As the water heats (up to 350 °C) it becomes less dense and more buoyant so it rises back to the surface. As the superheated water passes through the oceanic rocks it dissolves minerals and transports them to the surface where they are precipitated to form vents. Full name of DNA - ANSWER- deoxyribonucleic acid If DNA is required to make DNA, how could we have originally gotten DNA? - ANSWER- This problem may be solved by utilizing another molecule that can code information, RNA or ribonucleic acid. RNA has the advantage of being self-replicating, leading some to believe that the earliest life on Earth may have been RNA-based and not DNA-based. The earliest fossils that have been discovered to date are those of fairly advanced microbes. This means one of two things: - ANSWER- 1. Life was brought to Earth via Panspermia at that particular time and at that specific stage of development. However, this is unlikely as the fossils we find appear to have been very well adapted to conditions on Earth, something that would have taken time. 2. We are missing much of the early history of life on our planet. Much of this record has probably been removed by tectonic activity and erosion. Define anaerobic in the context of early life on earth - ANSWER- it lived in an environment with no free oxygen Define heterotrophic in context of early life on earth - ANSWER- Heterotrophic creatures do not synthesize their own food (like plants) but ingest it from the surrounding environment (like we do). Early life forms probably were this. Name the microbe that could be found in early life on earth - ANSWER- a prokaryote (an organism that lacks a cell nucleus or any great complexity of internal cell structure, lived in the early oceans, and "fed" on the organic compounds that were produced from inorganic constituents. Supply of AtP in the early ocean would have become depleted. Competition for it would have led to evolution of new strategies of nutrition and metabolism, such as____ - ANSWER- autotrophic bacteria. Autotrophs are organisms that produce complex organic compounds from simple inorganic compounds and energy. Name the strategy that was used next by life - ANSWER- Fermentation is probably the simplest autotrophic process that organisms could use so it follows that this was probably the strategy next used by life. Wher is the earliest fossil evidence found and what do they resemble? - ANSWER- The earliest fossil evidence is found in the Australian Apex Chert. Although somewhat controversial, these fossils are dated at 3.5 billion years and resemble modern day cyanobacteria, which are photosynthetic in nature. Hint that early life existed anywhere else? - ANSWER- There is the hint of photosynthesis at an earlier date in the Isua Formation, Greenland. Even though no fossils have been found there, the rocks at this location are enriched in isotopically light carbon isotopes (carbon 12), a signature of photosynthesis. Although an interesting possibility, this finding remains controversial; some have claimed that the isotopic signatures could be the result of later contamination. Define stromatolites - ANSWER- Stromatolites are mats of cyanobacteria (blue-green algae) that develop in shallow-water marine conditions. Along with the living material, these mats trap and bind sedimentary (inorganic) grains which help form layered domes of various shapes. The layers are built through time when the photosynthetic cyanobacteria tend to grow and move upwards towards the sunlight when covered by sediment. Where are the oldest stromotolites located? - ANSWER- The oldest stromatolites discovered so far are located in western Australia; these have been dated to be about 3.5 billion years old. During the Archean, stromatolites started to get larger and more complex. This change probably reflects the growth of the continents through this time period, which increased the area covered by shallow marine conditions where